mpd_oled/cava problem - no spectrum - and the fix

[mariusp44]

It was working fine in i20250309 but stopped working in the latest image. MPD information is displayed but spectrum analyzer is not working. This is only relevant if you are using spectrum OLED as I do:

There is an easy fix to this problem.

mpd_oled is started every time audio is played and stopped when audio finishes. It also starts cava that shows spectrum analyzer.

However, cava is not getting started properly and shows as defunct:

root        2104       1  0 21:35 ?        00:00:01   /usr/bin/mpd_oled -o 6 -f 25 -c fifo,/tmp/mpd.fifo
root        2172    2104  0 21:36 ?        00:00:00     [cava] <defunct>

mpd_oled runs under systemd and log shows:

Jul 11 21:05:13 daina mpd_oled[2844]: Error loading config. No HOME found (ERR_HOMELESS), exiting...

After some digging I found out that apparently cava requires HOME environment variable set and it is missing.
The fix is to modify mpd_oled systemd unit configuration adding HOME=/tmp:

1. Stop any audio that is playing
2. Run systemctl edit mpd_oled.service
3. Add the following lines right after first two comment lines:

[Service]
Environment=HOME=/tmp

4. Save and close.
5. Run systemctl daemon-reload to refresh systemd unit configuration

Play audio as you normally would - spectrum should display properly now and processes show cava is running as it should:

oot        2406       1  6 17:44 ?        00:00:01   /usr/bin/mpd_oled -o 6 -f 25 -c fifo,/tmp/mpd.fifo
root        2457    2406  4 17:44 ?        00:00:01     cava -p /tmp/cava_config_fgQm0W

[rern]

Thank you for sharing.